﻿#include"stack.h"

// 初始化栈
void StackInit(ST* ps)
{
	ps->arr = NULL;
	ps->top = ps->capacity = 0;
}

// 销毁栈
void StackDestroy(ST* ps)
{
	assert(ps);
	if (ps->arr)
	{
		free(ps->arr);
	}
	ps->arr = NULL;
	ps->top = ps->capacity = 0;
}

//栈是否为空
bool StackEmpty(ST* ps)
{
	assert(ps);
	return ps->top == 0;
}

// ⼊栈
void StackPush(ST* ps, STDataType x)
{
	assert(ps);
	if (ps->top == ps->capacity)
	{
		 int newcapacity = ps->capacity == 0 ? 4 : 2 * ps->capacity;
		 STDataType* temp = realloc(ps->arr, sizeof(STDataType) * newcapacity);
		 if (temp == NULL)
		 {
			 perror("realloc fail!");
			 exit(1);
		 }
		 ps->arr = temp;
		 ps->capacity = newcapacity;
	}
	ps->arr[ps->top++] = x;
}

//出栈
void StackPop(ST* ps)
{
	assert(!StackEmpty(ps));//栈顶不能为空
	--ps->top;
}
//取栈顶元素
STDataType StackTop(ST* ps)
{
	assert(!StackEmpty(ps));
	return ps->arr[ps->top-1];
}

//获取栈中有效元素个数
int StackSize(ST* ps)
{
	assert(ps);
	return ps->top;
}


